Hi head wax
I used to use Blacksmith Paint until the 3D paint in Carrara got jacked up - it would certainly produce better results than painting in Carrara because it makes an atlas UV map, so the paint doesn’t tend to try and follow the lines of the original UV mapping. I’m surprised that Carrara doesn’t offer this facility to go with 3D painting.
I’ve tried 3D painting a grid on M4, one shading domain at a time - can certainly match up the lines and the vertical stripes are straight, but the horizontal ones are jagged - used a 0.01 brush. Then there is the challenge of getting the lines to match all around the figure and you’d need a very good eye for proportions to get the spacing on the grid spot-on.
Also tried drawing the grid on an M4 template - probably can be done, but you’d have to be a genius and draw curved lines to make the lines come out straight on the figure. For instance, the seam for the torso is down the middle of the back and has a lot of curves - you’d need to draw two matching, curvy lines to make a line straight down the back.
I guess you could lay out the UV mapping differently, stitching it all together to make a new template - but that would be way more work than it’s worth.